THE FUNGI WHICH CAUSE PLANT DISEASE 11 



Spumariaceae (p. 10) 



Sporangia separate or sethalioid; calcarious deposit in the peri- 

 derm or columella, never in the capillitium; capillitium radiating 

 from various points of the columella, branching and anastomosing 

 to form a network, the ultimate branchlets of which support the 

 periderm. 



Key to Genera of Spumariaces 



Fructification of ordinary sporangia 1. Diachea. 



Fructification sethalioid 2. Spumaria, p. 11. 



Spumaria Fersoon 



Fructification ajthalioid, consisting generally of large cushion- 

 shaped masses covered without by a white foam-like crust; within, 

 composed of numerous tubular sporangia, developed from a com- 

 mon hypothallus, irregularly branched, contorted and more or less 

 confluent; the peridial wall thin, delicate, frosted with stellate 

 lime crystals, which mark in section the boundaries of the several 

 sporangia; capillitium of delicate threads, generally only slightly 

 branched, terminating in the sporangial wall, marked with oc- 

 casional swellings or thickenings. 



S. alba (Bui.) D. C. Like all other members of the order 

 the present species is not a parasite but its aethalia are fre- 

 quently produced upon grass, strawberries *^ and other plants in 

 such abundance as to cause more or less serious injury. The 

 sporangia are fused into a large jethalium which is white or cream- 

 colored, from 1 to 7 cm. long and half as thick. 



Physaraceae (p. 10) 



Key to Genera of Physaraceae 



Fructification sethalioid 1- Fuligo, p. 12. 



Fructification plasmodiocarpous or of distinct 

 sporangia 

 Peridium without lime 



Plasmodiocarpous 2. Cienkowskia. 



Sporangia distinct 3. Leocarpus. 



Peridium calcareous, more or less throughout 

 Capillitium calcareous throughout 4. Badhamia. 



